An often used commercial system for the separation of air is cryogenic rectification. The separation is driven by elevated feed pressure which is generally attained by compressing feed air in a compressor prior to introduction into a column system. The separation is carried out by passing liquid and vapor in countercurrent contact through the column or columns on vapor liquid contacting elements whereby more volatile component(s) are passed from the liquid to the vapor, and less volatile component(s) are passed from the vapor to the liquid. As the vapor progresses up a column it becomes progressively richer in the more volatile components and as the liquid progresses down a column it becomes progressively richer in the less volatile components. Generally the cryogenic separation is carried out in a main column system comprising at least one column wherein the feed is separated into nitrogen-rich and oxygen-rich components, and in an auxiliary argon column wherein feed from the main column system is separated into argon-richer and oxygen-richer components.
Often it is desired to recover product gas from the air separation system at an elevated pressure. Generally this is carried out by compressing the product gas to a higher pressure by passage through a compressor. Such a system is effective but is quite costly. It is also desirable in some situations to produce liquid product which may be used during high demand periods and for purposes other than the uses of the gas product.
Accordingly it is an object of this invention to provide an improved cryogenic air separation system.
It is another object of this invention to provide a cryogenic air separation system for producing elevated pressure product gas while reducing or eliminating the need for product gas compression.
It is yet another object of this invention to provide a cryogenic air separation system for producing elevated pressure product gas while also producing liquid product.